Faceted core

ABSTRACT

A plate element constructed to simulate a plurality of hexagonal pins aligned so that their center lines are in a common plane and such that adjacent pins abut at a common face. The edge of the plate element normal to the hexagonal pins is cut to exhibit three, mutually perpendicular, square, optical facets for each hexagonal pin. The facets in each group of three are parallel, respectively with the facets in every other group of three.

O Umted States Patent us] 3,649,153 Brudy 51. Mar. 14, 1972 [54] FACETED CORE [56] References Cited [72] Inventor: Peter E. Brudy, 224 California Avenue, UNITED STATES PATENTS Canada 3,417,959 12/1968 Schultz ..|s/44 x [22] Filed: Nov. 4, 1969 3,069,72l 12/1962 Ami et al. ..l8/44 UK [211 APPl- 873,935 Primary Examiner-H. A. Kilby, .lr.

, 1 Attorney-Thomas T. Rieder [30] Foreign Application Priority Data 57] ACT NOV. 4, Great Britain A plate element construcld o simulae a f hexagonal pins aligned so that their center lines are in a common [52] US. Cl. ..425/469, 249/ l 17 plane and such that adjacent pins abut at a common f The [51] ll?- Cl. edge of the plate element normal [0 the hexagonal pins cut [58] Field of Search ..249/1 17, 140, 187 R; l8/42 R, to exhibit three, mutually perpendicular, square, optical facets 18/42 D, 44 for each hexagonal pin. The facets in each group of three are parallel, respectively with the facets in every other group of three.

Patented March 14, 1972 3,649,153

2 Sheets-Sheet l VILVTHR.

E. BRUDY Agent Patented March 14, 1972 3,649,153

2 Sheets-Sheet 2 INVENTOR. PETER E. BRUDY BY M/A Agent FACETED CORE This invention relates to the manufacture of reflectors commonly referred to as central triple reflectors, the main feature of which is to reflect light back towards the source of the light, provided the path of incident light is not too wide of normal to the face of the reflector. Such reflectors are also sometimes referred to as retrodirective reflectors. The usual construction of such retrodirective reflectors includes a smooth outer surface (flat or curved) and an accurately formed inner surface constituted by reflecting surfaces or facets that intersect one another preferably at 90 angles in the form of cubic corners or prisms. Those familiar with the art will be well acquainted with this particular kind of prismie or faceted surface. Reflectors of this type are of particular use in automotive vehicles, along highways and airfield landing strips, and at other locations where they are useful as guides, indicators, or danger signals.

In order to permit the manufacture of such retrodirective reflectors, the standard procedure has been to provide a number of hexagonal metal rods having three substantially square facets ground and polished at one end, each facet being perpendicular to both other facets. Thus, the three facets define three contiguous faces of a cube. A large number of such hexagonal faceted metal pins is locked together to form a core with the points of all the hexagonal pins lying substantially in the same plane, and a clear plastic, such as clear acrylic, is molded against the multiplicity of facets provided by the core, to form a flat molded item having one surface smooth and the other surface faceted precisely complementally to the facets of the core.

In accordance with the specifications set forth by the Society of Automotive Engineers, there are two class divisions of reflecting devices of this kind; class A requiring visibility from all distances between 100 and 600 feet when illuminated by the upper beam; and class B requiring visibility from all distances between 100 and 350 feet, when illuminated by the upper beam. Color test requirements, according to the same code, also specify that the thickness of the reflecting lens be approximately twice the thickness of the section as measured from the smooth face of the lens to the apices of the reflecting planes.

The automotive manufacturers generally prefer to exclusively produce reflectors of class A brilliance. In order to provide such reflective brilliance, near perfection of angulation and alignment of cooperating elements is required. As well, the plane mirror surfaces must have a flatness no coarser than 1.5 X angstroms.

The accuracy of the reflector, and its subsequent brilliance, is wholly dependent upon the core face against which it is formed. Consequently, only those methods of forming the faces to the extent previously specified are considered acceptable.

One disadvantage of prior art methods of assembling the pins together relates to the difliculty, particularly when the pins are of small section, of accurately positioning the pins both longitudinally and in proper lateral orientation. The longitudinal alignment of the hexagonal pins is critical from the point of view of utilizing a minimal amount of material, because of the color test requirements mentioned above. It is also desirable, in order to minimize the material used, to reduce the lateral dimensions of the hexagonal rods, but hitherto a lower limit has been placed on the dimensions of the hexagonal rods because of the handling problems associated with setting a plurality of the rods up to form a core. The more handling, the greater the risk of damaging the very precisely ground optical facets on the ends of the rods, and the handling of small-section rods is more difficult than the handling of large-section rods.

Thus, due to the impracticality of using hexagonal rods of smaller section, and consequently of smaller cubical facets, it has not been possible to significantly reduce the amount of plastic material required for each lens, clue to the color test requirements set forth by the Society of Automotive Engineers, mentioned above.

In view of the above disadvantages of conventional methods in this field, the object of this invention is to make possible the fabrication of ultra-thin retrodirective reflectors, and thus to permit the economy which the use of such thin sections would entail. It will be appreciated that the possibility of utilizing less material per unit of surface area would permit automobile manufacturers, for example, to increase the reflective area on such items as tail lenses and side-reflectors, without increasing the cost of the material.

One embodiment of this invention is shown in the accompanying drawings, in which like numerals devote like parts throughout the several views, and in which:

FIG. 1 is a top plan view of a plate element utilized in this invention;

FIGS. 2, 3 and 4 are sequential views showing steps in the fabrication of the plate element of this invention;

FIG. 5 is a perspective view of several plate elements interlocked to form the faceted mold surface, with one of the plate elements being spaced from the rest;

FIGS. 6 and 7 are perspective views of core elements fabricated from the plate elements shown in the preceding figures;

FIG. 8 is a top plan view of the end portion of a plate element utilized in this invention, to a large scale; and

FIG. 9 is a top plan view of an unfaceted plate element to a smaller scale than FIG. 8.

Basically, this invention relates to, and has as its object, the fabrication of mold-cores for central triple reflectors which permit the production of reflecting lenses in thinner sections than previously practical.

It has been found that, using conventional methods, the lower limit for the distance between the flat or smooth surface of a reflector and the points or peaks between the cubical facets on the other side of the reflector is approximately 0.050 inches. This is due to the necessity for meeting the color test requirements mentioned above, and to the fact that, when utilizing individual hexagonal rods, it is not possible to maintain the accuracy and the optical qualities of the rods in smaller cross sections. With the present invention, it has been found possible to reduce the distance mentioned above by ap proximately two-thirds.

The basic concept forming the focus of this invention is the provision of a plate element 10, as seen in FIG. 4, which is fabricated to simulate precisely a plurality of hexagonal rods, each having cubical optical facets ground at one end, the rods being aligned and integral with one another at common hexagonal faces. In FIG. 8, a plan view of the end portion 11 of the plate element 10 can be seen. The end portion 11 has three contiguous cubical facets a, b and 0 ground at the end being viewed in FIG. 8, and the portion 11, in cross section, is a regular hexagon in which the distance X is the width of one side, which is also equal to the external radius X The internal radius Y is equal to 0.866X. The plate element 10 has vertical grooves of internal angle, as seen in FIG. 8, which shows the end portion 11 integral with the next-inward portion 12. FIG. 9 is a plan view of an uncompleted plate element 10 in which the contiguous faces 14 are at the angle of 120, and in which the distance D may be arbitrarily set, but is preferably greater than 0.030 inches.

In FIG. 1, the plate element 10 has edges 16, has vertical grooves 17 of 120 on either side, and has the end visible in plan in FIG. 1 ground and polished so as to form a plurality of cubically faceted points 18. In other words, three facets a, b and c meet at each of the points 18, and each facet is at right angles to the other two.

In FIG. 2 is shown a plate member I0 which embodies the grooves 17, but of which the upper end is flat and has not been ground and finished to the desired shape.

FIG. 3 is a perspective view of the same plate as is shown in FIG. 2, except that all the facets a and b have been ground, lapped and polished to the desired finish, while the plate is inclined at a suitable angle. The facets a and b are normal to one another and produce two sides of each of the cubical groups of facets. The facets a and b are finished in a single operation, and a small portion 21 of the upper outside edge remains ummachined.

FIG. 4 shows a finished plate which has ground and lapped facets completed on the outer side. The facets c are, of course, at right angles to both of the mating facets a and b.

It will now be obvious that the finished plate is the complete equivalent of a plurality of hexagonal rods with appropriately ground and lapped cubical facets at their ends, joined together edge to edge. This facilitates handling, and makes it extremely simple to position the plate properly with other similar plates to form a core. Such a core is shown in FIG. 5, in which five finished plates are shown in interlocked position, with a further plate element 25 in spaced relation thereto.

The process of fabricating the mold does not end with the fabrication of the plates, but requires proper orientation of numerous plates, the securing of these plates to each other, and to the base or body of the mold. Conventional means for such fastening would be the most simple and the most accurate. Preferably, such fastening would be by means of fusion-welding, arc-welding, or brazing the bases of the plates together, and subsequently drilling and tapping the core to take holddown bolts carried through the mold body. Highly acceptable welding and grinding techniques have already been developed and have proven satisfactory in the manufacture of cores formed of hexagonal rods with shaped ends. Such procedures specify cooling and ventilating the core during the welding process to avoid undesirable tempering of the metal, undesirable stress formation, and warpage of the material.

FIGS. 6 and 7 are for the purpose of showing two methods in which the core bundle may be assembled and subsequently shaped for introduction into the mold. FIG. 6 shows a series of plate elements 32 having suitably shaped faces 31 and forming a mold-core bundle 30. In this respect, the plate-system is far superior to the hexagon rod system, since the process of putting an angular slope on the sides 34 of the bundle 30 does not sever and release the outer plates. FIG. 7 shows a pair of plate bundles 40 which have the required faces 41 for molding and are formed in such a manner as to complement each other in the mold body by being joined together at the bevelled faces 42 shaped for this purpose. In FIG. 7, it should be noted that the plates 43 are themselves tapered vertically in order to provide the desired shape, thereby avoiding extensive machining after the fastening process is completed. The core faces 41 are shown as being very fine, to indicate further the possible minimization of the matrices which this system afiords the core-maker, and the molder.

Numerous techniques have been developed over the years for the manufacturing of molding elements which serve to form central triple reflectors. Notable advances are the development of lapping and polishing methods which make the fabrication of class A reflectors readily attainable. As well, techniques have been developed which permit the simple fastening of multielement units by inert-gas welding. However, no system has yet been developed which is comparable to the present invention with respect to ease of fabrication, ease of handling, ease of fastening and shaping, and especially in the flexibility of dimension which it affords the user.

The plate-elements of this invention can be formed by extruding, rolling, casting, powdered metal fonning, and the like. It is preferred to use a system in which the plates are rolled on a continuous basis, and after being severed at a desired length, they are then placed in a compression or percussion die, having highly accurate and well hardened forms, such that the impact will serve to impart to the plate the highly accurate features of the die masters.

Since, as mentioned above, it is necessary to finish the two facets a and b (see FIGS. 3 and 4) in a single operation, as opposed to the flat lapping and polishing utilized with the conventional hexagonal rod assemblies preference is naturally given to the use of diamond tools.

To cut the facets aand b, a number of unfinished plates (see FIG. 2) are stacked alternately with spacers between each pair, such that the apices of the V-grooves are aligned, the stack forming an angle to the work surface of ideally 5444. A tool is then passed through the plates at the narrowest points, said tool cutting the facet at angle of 45 to the work surface, and for highly accurate results the tool cuts both facets a and b simultaneously, at to each other, and at 45 to the work surface, upon which the assembly lies. This procedure is referred to as the first cut.

' The plates are then rotated 90, and at an angle to the work surface of ideally 3516, the remaining facets c are cut, and for this process no spacers are necessary, since the plates are interlocked together. This step is referred to as the second cut.

As mentioned above, it is possible to form a wedge-shaped core by providing plate elements which are themselves tapered in the direction away from the optical facets. If all of the plates are tapered to the same degree, there will be produced a curved core face, and therefore a curved, but optically accurate, reflector face. For such a process, the second cut angle must be decreased by the angle of taper of each plate, which is calculated by the formula:

360/7I'D/P where D is 2 times the radius of the reflector core, and Pis the distance across the hexagonal flats of the plates.

I claim:

1. For use in fabricating a core for the molding of central triple reflectors, a plate element shaped to simulate a plurality of hexagonal pins aligned such that their center lines are in a common plane and such that adjacent pins abut at a common face, the edge of the plate element which corresponds to one end of the simulated hexagonal pins having three mutually perpendicular, square, optical facets for each simulated hexagonal pin, the three facets of one simulated hexagonal pin being parallel, respectively, with the three facets of every other simulated hexagonal pin, the central axis of each simulated pin defining the same angle with every facet 2. A core for the molding of central triple reflectors, the core comprising a plurality of plate elements, each plate element simulating a plurality of hexagonal pins aligned such that their center lines are in a common plane and such that adjacent pins abut at a common face, the edge of the plate element which corresponds to one end of the simulated hexagonal pins having three mutually perpendicular optical cubical facets for each simulated hexagonal pin, the three facets of one simulated hexagonal pin being parallel, respectively, with the three facets of every other simulated hexagonal pin, the central axis of each simulated pin defining the same angle with every facet.

3. For use in fabricating a core for the molding of central triple reflectors, a plate element having a plurality of parallel V- grooves on each face, each V-groove having two flanks set at l20 and equal in width, all V-grooves being identical, the V- grooves on opposite sides of the plate element being positioned opposite one another, the apex of each V-groove being spaced from the apex of the opposing V-groove by a distance equal to the width of a flank, one of the edges of the plate element perpendicular to the V-grooves defining a plurality of square optical facets arranged in groups of three mutually perpendicular facets each, the apices of opposing V-grooves dividing one group from another, a hypothetical line parallel with the V-grooves defining the same angle with every facet.

4. The invention claimed in claim 2, in which the plate elements of the core are interlocked so that the optical cubical facets define a faceted surface against which a central triple reflector can be molded, the core being substantially rectangular as viewed looking into the optical cubical facets and thus having two pairs of opposing edges adjoining the faceted surface, one said pair of opposing edges being tapered convergingly away from said faceted surface.

S. For use in fabricating an arcuate-surface core for the molding of central triple reflectors, a plate element shaped to simulate a plurality of substantially hexagonal pins aligned such that their center lines are in a common plane and such that adjacent pins abut at a common face, the plate element perpendicular while the third of the three facets lies in a plane which defines, with a hypothetical plane perpendicular to both of the mutually perpendicular facets, an angle given by the formula:

360 P /1rD where P is the distance across the hexagonal flats of a given simulated pin, and D is twice the radius of said arcuate-surface core, the latter radius being defined as the distance from the facets to the point of convergence of the plate element.

t i i 

1. For use in fabricating a core for the molding of central triple reflectors, a plate element shaped to simulate a plurality of hexagonal pins aligned such that their center lines are in a common plane and such that adjacent pins abut at a common face, the edge of the plate element which corresponds to one end of the simulated hexagonal pins having three mutually perpendicular, square, optical facets for each simulated hexagonal pin, the three facets of one simulated hexagonal pin being parallel, respectively, with the three facets of every other simulated hexagonal pin, the central axis of each simulated pin defining the same angle with every facet.
 2. A core for the molding of central triple reflectors, the core comprising a plurality of plate elements, each plate element simulating A plurality of hexagonal pins aligned such that their center lines are in a common plane and such that adjacent pins abut at a common face, the edge of the plate element which corresponds to one end of the simulated hexagonal pins having three mutually perpendicular optical cubical facets for each simulated hexagonal pin, the three facets of one simulated hexagonal pin being parallel, respectively, with the three facets of every other simulated hexagonal pin, the central axis of each simulated pin defining the same angle with every facet.
 3. For use in fabricating a core for the molding of central triple reflectors, a plate element having a plurality of parallel V-grooves on each face, each V-groove having two flanks set at 120* and equal in width, all V-grooves being identical, the V-grooves on opposite sides of the plate element being positioned opposite one another, the apex of each V-groove being spaced from the apex of the opposing V-groove by a distance equal to the width of a flank, one of the edges of the plate element perpendicular to the V-grooves defining a plurality of square optical facets arranged in groups of three mutually perpendicular facets each, the apices of opposing V-grooves dividing one group from another, a hypothetical line parallel with the V-grooves defining the same angle with every facet.
 4. The invention claimed in claim 2, in which the plate elements of the core are interlocked so that the optical cubical facets define a faceted surface against which a central triple reflector can be molded, the core being substantially rectangular as viewed looking into the optical cubical facets and thus having two pairs of opposing edges adjoining the faceted surface, one said pair of opposing edges being tapered convergingly away from said faceted surface.
 5. For use in fabricating an arcuate-surface core for the molding of central triple reflectors, a plate element shaped to simulate a plurality of substantially hexagonal pins aligned such that their center lines are in a common plane and such that adjacent pins abut at a common face, the plate element tapering convergingly away from the edge corresponding to one end of the hexagonal pins, said edge corresponding to said one end of the hexagonal pins having three optical facets for each simulated hexagonal pin, the optical facets of the plate element being so arranged that two identical such plate elements when interlocked define at said one end a plurality of cubically faceted recesses, each recess being defined by three mutually perpendicular facets.
 6. The invention claimed in claim 5, in which, for each simulated hexagonal pin, two of the three facets are mutually perpendicular while the third of the three facets lies in a plane which defines, with a hypothetical plane perpendicular to both of the mutually perpendicular facets, an angle given by the formula: 360 P / pi D where P is the distance across the hexagonal flats of a given simulated pin, and D is twice the radius of said arcuate-surface core, the latter radius being defined as the distance from the facets to the point of convergence of the plate element. 